1. Field of the Invention
The present invention relates to a process for the arylation of olefins by reaction of haloaromatics or arylsulfonates with olefins in the presence of a palladium catalyst and a bulky nitrogen base, if appropriate in a dipolar aprotic solvent.
2. Background of the Invention
Many aryl olefins have great industrial importance as fine chemicals, UV absorbers, starting materials for polymers and intermediates for active compounds.
The preparation of arylolefins is frequently carried out by means of palladium-catalyzed coupling of iodoaromatics or bromoaromatics, and to a lesser extent chloroaromatics or arylsulfonates, with olefins. Owing to the high price of iodoaromatics and bromoaromatics and the large amounts of waste product caused by the high molar masses, their use on an industrial scale is disadvantageous. However, the more readily available and therefore more attractive chloroaromatics have a comparatively low reactivity.
Littke and Fu (J. Am. Chem. Soc. 2001, 123, 6989) describe a process in which chloroaromatics are reacted with olefins at room temperature using palladium-dibenzylideneacetone ([Pd2(dba)3]) and tri-tert-butylphosphine in the presence of dicyclohexylmethylamine in dioxane. However, the turnover numbers (TONs) are low and large amounts of palladium catalyst are required for the process described, which makes its industrial application uneconomical.
There was therefore a need to develop a process which makes it possible for haloaromatics, in particular chloroaromatics, to be coupled with olefins in an efficient way.